The Internet Protocol (IP) includes the rules and encoding specifications for sending data. Layer 3 of the open systems interconnect (OSI) model is the network layer in which protocols such as IP operate. Layer 3 and above services are generally deliverable via Ethernet physical connections. To meet user expectations for high quality Ethernet services, such as differential mode pseudo-wire, a method of monitoring packet performance, such as one-way latency, is required. One-way latency and other performance measurements require a clock reference with a high degree of accuracy.
Communications between packet networks and time domain multiplexing (TDM) or synchronous systems may further complicate performance tracking. Many existing systems and interfaces, such as Ethernet switches, do not provide a cost efficient, robust, and reliable system for maintaining a clock or timing signal.